Supramolecular polymers via nucleobase directed self-assembly of low-molecular weight monomers

Material properties of small molecules can be drastically altered by the use of supramolecular polymerization, i.e. the self-assembly of small molecules into polymer-like materials though the use of the non-covalent bond. A simple way to achieve supramolecular polymers is by attachment of appropriate supramolecular motifs to the ends of a core unit. The backbones of the resulting polymeric systems will therefore contain non-covalent bonds, in addition to covalent bonds, which imparts upon the system reversibility and temperature sensitivity. Our investigations in this field have focused on the use of DNA nucleobase pair interactions to control the self-assembly of various low molecular weight monomers into polymeric architectures. Our work has focused on initial studies on the use of N-protected-nucleobase derivatives as the molecular recognition motifs. The use of protected rather than natural nucleobases allows for additional structural control to be built into the systems. We have prepared a series of supramolecular telechelic monomers, where nucleobase derivatives were attached to the ends of a variety of cores. Initial investigations involved rigid mesogenic/photoluminescent cores. Attachment of thymine and N6-anisoyl adenine to the ends of a alkoxy(bisphenylethynyl)benzene core produced monomers with high melting temperatures and no apparent liquid crystalline behavior. Mixing and annealing of the two monomers resulted in self-assembly accompanied by a dramatic decrease in melting temperature concurrent with the formation of liquid crystalline phases. In addition, the resulting material allowed for the formation of fibers which were photo luminescent. In the second system we utilized a soft polytetrahydrofuran as our central core. This macromonomer system also self-assembled into polymeric materials exhibiting a variety of material properties which were dependent on the type of terminal nucleobase that was attached. A dramatic increase in melting temperature occurred upon attachment of a terminal nucleobase compared to unfunctionalized polytetrahydrofurans. In addition, these materials also formed films and fibers. Finally, we utilized short methylene chains as our cores, in order to aid the self-assembly of monomers on a hydrophobic surface. In this case we observed the formation of very unique patterns which were modeled to determine the specific assembly motif. This thesis will report on the analysis of all three of these supramolecular systems.